There were three different RF transistors used in those "preselectors" as they
were referred to by "M". I wondered if you were aware of that? The first was a
M4605, a Germanium PNP manufactured by Philco and used in a bridge neutralized
circuit. The next was a M9108, a Ge PNP manufactured by Mot. SPD also in a
bridge neutralized circuit, and the last was a M9223, a Ge PNP manufactured by
Texas Instruments also in a bridge neutralized circuit. Now Skipp, which one
did you find to work the best for you? They were used in the TLD 6262A, TLD
6283B and TLD 6821A.
The best was probably was the HB Dispatcher rcvr preselector, TLD 6321A which
used a M9405 Ge PNP selected from the M9223 and had a silver plated casting
whereas the Motrac rcvrs had an alboloy plating.
The TLD 6881A RF preamp designed for use in the HB Motrac rcvr also used a
M9223 in a bridge neutralized circuit, but was found to oscillate at
frequencies 10 or 15 MHz or so below the frequency it was tuned to. Have you
ever found this to be happening?
The Research line was the HB Sensicon receiver.
AC
skipp025 <[EMAIL PROTECTED]> wrote:
Motohead (Motorola) had semi global names for some of their
equipment lines although you didn't see them mentioned as much
as you would expect.
"Research Line" was one such name although I'm not sure of the
dates and equipment it was assigned to describe. Probably the
wonderful Sensicon Receiver era where burnde finger tips from
trying to pull tubes was the order of the day.
The cast preselector (with bipolar preamp) you mentioned is a real
nice animal to use for some special applications. The bi-polar
transistor preamp holds it's own against even some of the more modern
preamplifiers in regards to decent 3rd order performance. I still
pull and save them for projects them when it's easy to remove and
store them away.
cheers,
skipp
> allan crites <[EMAIL PROTECTED]> wrote:
> allan crites <[EMAIL PROTECTED]> wrote: Date: Wed, 23 May 2007 16:51:22
-0700 (PDT)
> From: allan crites <[EMAIL PROTECTED]>
> Subject: Motrac Rcvrs & PL encoder / decoders
> To: Repeater-Builder@yahoogroups.com
>
> Kris and John,
> There were no Motorola Motrac base stations built. Only beige
colored " upright" ( as they were referred to at Motorola)
transistorized models which were developed after the Motrac mobile
development (which stations had two tubes in the xctr and one or two
tubes in the PA depending on the output power and power supply) which
was called instant death at Mot. because of no switching relay heard
when the PA B+ was switched on.
> Many confuse the " upright" base station with the Motrac mobile
because of the casting used in the mobile was the same as one used in
the base rcvr. If one follows the history of the transistorized rcvr
used in the mobile, one will find it was adapted for use in the base
sta.rcvr with a variety of audio pcb's depending on the application
and which were not interchangeable with mobile models.
> The original Motrac rcvrs, low band, high band, and 450 models,
had heated xtals, ( 25-45 MHz for LB, 28-32 MHz for HB, and 48-49 MHz
for the 450's) had the designation "H" in the model number and the 1st
mixer was a diode. A later "H" HB version had heated 36-39 MHz xtals.
The HB "L" rcvr came next with a preselector casting and with a
bipolar transistor mixer, and the heated xtals were replaced with the
channel element. The HB and 450 "M" versions were designed as having
an FET in the 1st mixer along with a xtal filter in the 8 MHz IF HB
and a 11.7 MHz xtal filter in the 450 version.
> There was also a Motorola rptr station designed with a 450MHz "M"
rcvr replacing the "B" tube type rcvr in the L44BBB-3100A station.
> Along the same time frame was a Compa Station designed using the
Motrac mobile xmtr and rcvr in a short cabinet and a side mounted PS
followed by a Consolette station also using a mobile xmtr and rcvr
with a horizontal AC PS, in all LB, HB, and 450 models.
> All this time the rcvr audio pcb underwent many revisions.
> Kris- If the rcvr in your station is a TLN 6962A it is obviously a
CS model and the audio pcb is not convertible to use the original
copper PL reeds. If you have the TLN 6966A then the rcvr should have a
reed socket mounted on the front of the rcvr casting.
> You need to have an in depth look at what you have.
> I suggest an external PL encoder/ decoder as it would be more
versatile for your applications.
> WA9ZZU
>
